Molecular cloning and functional characterization of rat Delta-6 fatty acid desaturase

Mammalian cDNA fragments putatively encoding amino acid sequences character istic of the fatty acid desaturase were obtained using expressed sequence t ag (EST) sequence informations. These fragments were subsequently used to s creen a rat liver cDNA library, yielding a 1573-bp clone. Expression of DNA fragment containing either of two possible open reading frames (nucleotide numbers 97-1431 and 148-1431) of the isolated clone in yeast led to the ac cumulation of gamma-linolenic acid in the presence of exogenous linoleic ac id. In this system, the addition of alpha-linolenic acid also resulted in t he accumulation of its Delta-6 desaturated product whereas dihomo-gamma-lin olenic acid failed to be a substrate. These results indicate that the prote in encoded by the rat cDNA is Delta-6 fatty acid desaturase, and the first 17 amino acids corresponding to the coding region 97-147 of the clone are n ot required to function in yeast. (C) 1999 Academic Press.